1. Field of the Invention
The present invention relates to a light shielding structure of an optical device such as a lens barrel having two annular members which move relative to each other in an axial direction.
2. Description of the Related Art
Optical devices, especially lens barrels which move between a retracted state (non-operating state) and a ready-to-photograph state (operating state) are usually provided with a number of annular members which move relative to one another in an axial direction. The lens barrel must be provided, between two annular members among the number of annular members which serve as exterior members of the lens barrel, with some sort of light shielding structure. This sort of light shielding structure is disclosed in, e.g., Japanese Unexamined Patent Publication 2007-183685.
This light shielding structure has been formerly designed based on a design principle of simply filling a clearance between two annular members with a light shielding member (e.g., light shielding paper, fabric or Mylar). However, a sliding frictional resistance (contact resistance) occurs due to the light shielding member when the two annular members move relative to each other. It is desirable to reduce such sliding frictional resistance between the light shielding member and the annular members as much as possible in order to reduce the load on relative movement between the two annular members. In addition, since sliding frictional resistance continuously occurs during relative movement between the two annular members, there is a possibility of fine scuffs being made on a periphery of the annular member which is in sliding contact with the light shielding member.